"A guide to sending email" matching MCP servers:

Enables sending transactional emails with text or HTML body, delivery status, and message ID via Resend. Pay-per-call using x402 micropayments (USDC on Base L2), no API key or signup required.

A pre-payment safety gate for x402 that screens payment metadata for PII, enforces spending policies, and detects replay attacks before signing.

Pay-per-call USDC payment proxy for AI agents. Issue scoped Pay Tokens with hard spending caps and auto-journal every charge to freee / Money Forward / QuickBooks.

A paid MCP server that lets AI agents send SMS messages to US phone numbers via x402 micropayments, with automatic compliance and opt-out handling.

Enables AI agents to discover and pay for x402-gated HTTP APIs, handling 402 Payment Required flows with local signing. Supports EVM and Solana with non-custodial wallet management.

Keyless crypto payments for AI agents. One MCP call turns any wallet address into a non-custodial crypto payment link or tip jar, no API key and no account, with funds settling straight to your wallet at a 0% platform fee (USDC/USDT, BTC, LTC, DASH, DOGE, ZCASH).

A read-only MCP server for the open-banking.io PSD2 API that lets AI agents query personal bank balances and transactions via natural language, with zero-knowledge encryption ensuring all sensitive data is decrypted in-process and never exposed to third parties.

x402-trust gives AI agents a "check before you pay" layer for the x402 ecosystem.

Enables AI agents to search marketplace listings, place escrow-protected purchases paid in Nano, track orders, and retrieve signed receipts.

A template for building MCP servers with a built-in paywall gate that offers free local execution and premium server-side execution via Stripe and x402 payment lanes.

Enables running a local MCP server for Poland's KSeF (Krajowy System e-Faktur) e-invoicing system, so invoice data stays on the user's own machine rather than passing through an intermediary service. It currently exposes only a diagnostic server_info tool, with invoice search and retrieval tools still to come.

Create free, no-signup invoices from your AI assistant — the create_invoice tool returns a link that opens blankinvoicemaker.com pre-filled, ready to download as a watermark-free PDF.

MCP server exposing a fictional payment domain as tools, resources, and prompts, enabling reasoning over transactions, payment hubs, services, and system health.

Enables AI agents to scan payment endpoints for safety, returning a letter grade (A–F) and verdict before authorizing payments.

A Model Context Protocol server that enables interaction with Monobank API, providing tools for currency exchange rates, client info, and account statements.

Enables AI agents to manage a fictional B2B workspace SaaS (Tessera) with tools for ticketing, invoicing, customer management, and trial extensions, featuring a human-in-the-loop confirm pattern for safety.

Enables AI agents to discover, inspect, and pay for paid HTTP and MCP services using USDC on Solana with a self-custodial wallet.

Connects Claude to the customer side of Housecall Pro, letting you view estimates and invoices, check company details, and decline estimate options using the link your contractor sent.

Exactly-once execution for irreversible agent actions: an agent claims the right to run an effect, and a retry after a lost response returns the sealed result instead of charging again. 12 tools over stdio, including a gateway mode where the agent holds a single-use ticket and never the provider key.

Non-custodial USDC <-> bank for AI agents. Free quotes; $0.05 USDC per session via x402; 1% commission itemised in every quote. Own funds only. PT + EU/EEA (not UK). 18+.